In the dark a glimmering light is often sufficient for the pilot to find the polar star and to fix his course. To the pilgrim often a single footstep suffices to enable him to find his way across the bewildering plain.

The fiery lava in the hollow bosom of the earth, if it be restrained, in spite of its prison, bursts forth with greater force; then flows abroad, but, as it flows, subverts, beats down, and overthrows plains, mountains, forests, and cities.